1. Field of Invention
This invention relates to biofeedback equipment, specifically to an improved mechanism for measuring the difference in skin temperature at two different points on the body.
2. Description of Prior Art
Biofeedback generally refers to an area of psychophysiological research and applications in which a subject learns to exert conscious control over certain autonomic systems. In general, the bioelectric signal generated by a specific physiological change is amplified, and the information concerning the change is fed back to the subject in a form that allows the subject to monitor the change, and thereby learn to control the function.
Biofeedback of skin temperature is an important technique in helping people deal with various problems, including anxiety, headache, backache, and other pain. It is also used in relaxation training, which is often employed in pain management programs (Gatchel and Turk, 1996), in the treatment of phobias and ADD (attention deficit disorder, also known as ADHD or attention deficit hyperactivity disorder), and for enhancing sports performance and meditation. The typical procedure is to teach people to warm their hands by providing biofeedback of hand temperature. Hand warming indicates peripheral vasodilation (dilation of blood vessels in the hand), and is related to relaxation. Conversely, hand cooling indicates peripheral vasoconstriction (constriction of blood vessels in the hand) and indicates a reaction to pain or anxiety. Relaxation and pain thus have opposite effects on hand temperature.
Several factors confound the use of simple hand temperature as a measure of pain or relaxation, however. The first factor is ambient room temperature. For example, decreasing room temperature can lead to decreased hand temperature. More importantly, the "orienting reflex" or simple orienting to a novel stimulus causes peripheral vasoconstriction (Sokolov, 1963). The object of the present biofeedback device is to provide a better way to measure the physiological response to relaxation or pain, which is not confounded by ambient temperature or by responses such as the orienting reflex.
The physiological response to pain or other aversive stimuli is called the "defensive reflex", and includes vasodilation in the head as well as peripheral vasoconstriction. The combination of peripheral vasoconstriction and cephalic vasodilation (head warming) distinguishes the defensive reflex from the orienting reflex (Razran, 1961). Thus a more effective measure of pain or relaxation would employ thermal biofeedback of both head and hand temperature. Pain leads to an increase in head minus hand temperature, and relaxation leads to a decrease in that difference. This measure would also control for ambient room temperature, which would have about the same effect on head and hand temperature.
A previous invention, U.S. Pat. No. 3,942,516 (1976) to Glynn and James, proposed a biofeedback method and system that includes a module for measuring the difference in skin temperature between two different locations on the body. However, this invention is complex, including sampling units, amplifiers and digital processors. It also includes three other feedback modalities, EMG, EEG, and "Other", and a matrix module to integrate the information from all the feedback modalities. Because of its complexity, this invention is relatively large and expensive. The typical use is in a therapist's office, with the assistance of the therapist to set up the equipment and guide the subject. It would be difficult for an average person to purchase and use the equipment himself or herself. Moreover, the equipment could not be carried about and used whenever and wherever it is needed.